5,395 research outputs found

    Environmentally-induced discharge transient coupling to spacecraft

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    The Hughes SCREENS (Space Craft Response to Environments of Space) technique was applied to generic spin and 3-axis stabilized spacecraft models. It involved the NASCAP modeling for surface charging and lumped element modeling for transients coupling into a spacecraft. A differential voltage between antenna and spun shelf of approx. 400 V and current of 12 A resulted from discharge at antenna for the spinner and approx. 3 kv and 0.3 A from a discharge at solar panels for the 3-axis stabilized Spacecraft. A typical interface circuit response was analyzed to show that the transients would couple into the Spacecraft System through ground points, which are most vulnerable. A compilation and review was performed on 15 years of available data from electron and ion current collection phenomena. Empirical models were developed to match data and compared with flight data of Pix-1 and Pix-2 mission. It was found that large space power systems would float negative and discharge if operated at or above 300 V. Several recommendations are given to improve the models and to apply them to large space systems

    Marine Managed Areas Workshop report, Penang, Malaysia, 18-19 January, 2011

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    Establishment of a working group of regional experts in Marine Protected Areas (MPAs); inventory and status of existing MPAs; gap analysis;establishment of common data requirements and protocols;development of a regional action plan;training and capacity building; outreach activities; proposal f0r management of existing and creation of new MPAs

    Ultra Wideband Channel Characterization and Ranging in Data Centers

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    This paper presents a detailed measurement based characterization of the Ultra Wideband (UWB) channels in a data center environment and examines the accuracy of direct ranging using Time of Arrival (ToA) measurements. Modern data centers present a unique indoor environment that to our knowledge has not yet been characterized. Our ranging experiments indicate that it is possible to achieve an accuracy of fraction of a meter via direct ranging and point to the feasibility of locating individual servers using more sophisticated cooperative ranging

    Involvement of extension personnel in implementing social forestry programmes

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    In a country like India, where the population is high and resources are limited, social forestry is an instrument for rural development, particularly for the poor people. Thus social forestry is identified as a forestry of the people, by the people and for the people

    Report of the Marine Protected Areas Working Group meeting, Penang, Malaysia, 11-12 February, 2014

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    The objectives of the workshop were to review and update Marine Protected Area (MPA) data, finalise policy briefs for each country and recommend future actions and policies for sustainable management of MPAs

    Spin-Hall effect and circular birefringence of a uniaxial crystal plate

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    The linear birefringence of uniaxial crystal plates is known since the 17th century, and it is widely used in numerous optical setups and devices. Here we demonstrate, both theoretically and experimentally, a fine lateral circular birefringence of such crystal plates. This effect is a novel example of the spin-Hall effect of light, i.e., a transverse spin-dependent shift of the paraxial light beam transmitted through the plate. The well-known linear birefringence and the new circular birefringence form an interesting analogy with the Goos-H\"anchen and Imbert-Fedorov beam shifts that appear in the light reflection at a dielectric interface. We report the experimental observation of the effect in a remarkably simple system of a tilted half-wave plate and polarizers using polarimetric and quantum-weak-measurement techniques for the beam-shift measurements. In view of great recent interest in spin-orbit interaction phenomena, our results could find applications in modern polarization optics and nano-photonics.Comment: 16 pages, 8 figures, to appear in Optic

    Hypohidrotic Ectodermal Dysplasia with total anodontia: a case report

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    Ectodermal dysplasia is a hereditary disorder that occurs as a consequence of disturbances in the ectoderm of the developing embryo. The triad of nail dystrophy, alopecia or hypotrichosis and palmoplantar hyperkeratosis is usually accompanied by a lack of sweat glands and a partial or complete absence of primary and/ or permanent dentition. A case report illustrating the prosthetic rehabilitation of a seven year old boy with hypohidrotic ectodermal dysplasia associated with total anodontia is presented

    Long-Range Navigation on Complex Networks using L\'evy Random Walks

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    We introduce a strategy of navigation in undirected networks, including regular, random, and complex networks, that is inspired by L\'evy random walks, generalizing previous navigation rules. We obtained exact expressions for the stationary probability distribution, the occupation probability, the mean first passage time, and the average time to reach a node on the network. We found that the long-range navigation using the L\'evy random walk strategy, compared with the normal random walk strategy, is more efficient at reducing the time to cover the network. The dynamical effect of using the L\'evy walk strategy is to transform a large-world network into a small world. Our exact results provide a general framework that connects two important fields: L\'evy navigation strategies and dynamics on complex networks.Comment: 6 pages, 3 figure
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